The present invention relates to a vaulted tank and, more particularly, to an above-ground storage tank for flammable liquids.
Since the 1970s, the world and the United States have been concerned with the environment and the contamination of that environment, including the earth""s soil, its atmosphere and its water. The first Earth Day in 1970 resulted in the eventual creation of the Environmental Protection Agency by the United States Congress.
One of the many problems which the Environmental Protection Agency has addressed is the deterioration of large, underground storage tanks which result in the leakage of contaminants into the soil, such as the deterioration of gas station storage tanks and the leakage of gasoline and diesel fuel into the surrounding water table.
To correct this problem, the EPA has suggested that all fuel storage tanks be placed above ground. This has created a classic confrontation between governmental departments. For example, the fire departments of most major cities prefer that fuel storage tanks be placed below ground to reduce fire hazard. Most municipal codes have been drafted with this concern in mind. In more recent years, the creation of large concrete entombed tanks has been suggested as a solution to the problem. That is, a gasoline storage tank may be entombed in concrete and placed above the ground to enable its surfaces to be easily checked for deterioration and fluid leakage. By entombing the fuel tank in concrete, the tank is made impervious to impact from a vehicle that might back into it, for example, and resistant to fire due to the insulating ellect fo the concrete. One example of such an entombed tank is shown in U.S. Pat. No. 4,826,644, issued May 2, 1989 to T. R. Lindquist and R. Bambacigno.
The concrete entombed tank has several disadvantages including cost and convenience. For example, a 1,000-gallon concrete entombed tank weighs 18,000 pounds after it has been manufactured. Such a tank requires a large truck and crane with at least two 20-ton nylon straps to transport the tank to the site where it is to be used and to then place the tank in the desired position. The concrete entombed tank is provided with bottom supporting feet to permit the inspection of its bottom surface during its use. In California, where earthquakes represent a real concern, concrete shoes are placed on the site on either side of the bottom supporting feet to prevent the movement of the tank during an earthquake. The placement of the concrete tank between the concrete shoes can be a very dangerous procedure in view of the tank""s weight.
Accordingly, it is an object of the present invention to provide a less expensive, lighter weight and more easily transported tank vault for the above-ground storage of liquid fuels, such as gasoline and diesel fuel.
This object and other objects are accomplished by providing an inner tank having a bottom surface, side surfaces, and a top surface which is placed within an outer shell having a bottom surface, side surfaces, and an open top. The bottom surface of the inner tank is spaced apart from and connected to the bottom surface of the outer shell by first, bottom spacers which do not extend to the side surfaces of either the inner tank or outer shell. The side surfaces of the inner tank and outer shell are spaced apart and attached to one another by second side spacers which do not extend to the bottom surface of either the inner tank or outer shell. The side spacers function to prevent the inner tank from floating within the outer shell when an insulating material, such as concrete, is placed therebetween.
The utilization of an inner tank and outer shell with appropriate bottom and side spacers for attaching the two permits the assembled tank to be shipped from the factory to the site where it is intended for use with relative ease because of its light weight. Once properly placed upon the site, the space between the inner tank and outer shell can be filled with a suitable insulation material to meet the strength and insulation requirements of the fire codes of all metropolitan areas. Spacing feet on the bottom surface of the out shell permit all surfaces of the tank vault to be inspected to assure that the tank does not deteriorate and leak. This meets the requirements of the Environmental Protection Agency.